Thanks to all who participated.
Yes, the "rank-1 method" is billed as "Broyden's rank-a method", altho that does not make it any clearer to me. And, as you pointed out, it won't be clear to many users, either. So I'll have to either say more or say less about it.
As far as how frequently the Jacobian gets updated, I guess that depends on the details of the problem and the guessed starting-point. I do have a toy problem (only 3 simultaneous equations in 3 variables) where the number of iterations made is 12, but the number of Jacobian evaluations is 1. So apparently the initial Jacobian was never updated. That did not affect the validity of the solution, however, as it satisfied the 3 equations to at least 8 significant figures.
BTW, I'm sure you all are annoyed at the excess question-marks. Does anyone know how to get rid of them when using Yahoo mail on IE 9? I have tried several things, but none seem to be successsful. Gimme some credit for trying, but little for succeeding.
Bob H
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